Method for the controlled removal of foreign gases from a sorption device with an inert gas trap

ABSTRACT

The invention concerns a method which enables an inert gas to be removed from an inert gas trap during operation of a sorption machine, in particular an absorption machine, thus ensuring improved control of the removal.

Prior Art

Sorption devices, particularly sorption refrigerating machines, are known in the prior art.

Materials and substances located in a sorption system may outgas or, for example, release gases due to chemical conversion. These disruptive gases or vapors prevent a quick sorption process, since they render access of the vaporous working medium to the sorption agent difficult during adsorption or absorption and prevent or render difficult access of the vaporous working medium to the condensation surfaces, both of which lead to an extreme retardation of the generation of cold and heat. This results in a substantial decrease in the performance of these sorption systems. The term “disruptive gas” refers here very generally to substances that influence the access of the working medium vapor to the sorption agent, thus preventing the sorption process (for example, carbon dioxide, nitrogen, etc.). The gases are also referred to as inert gases or foreign gases. These substances can be presorbed in the sorption agent, released through chemical reactions, outgas from the existing housing materials or occur through leaks in the system. In summary, in such low-pressure sorption devices, the problem therefore always exists that either outgassing or leaks might lead to a rise in pressure and thereby to a functional impairment of the device.

Processes and methods for removing an inert gas from a sorption machine, particularly an adsorption machine, are described in the prior art. For example, DE 103 10 748 B3 explains that foreign gases are removed upon detection of the gases in the system of an adsorption refrigeration machine.

DE 44 44 252 B4 describes a method in which a binding agent is introduced into the sorption machine. In order to maintain the system free of disruptive inert gas or vapor for the sorption process so that only working medium vapor is present in the vapor phase, a binding agent is added to the sorption system. The task of the binding agent is to bind the inert gases or vapors present or released in the sorption system, thereby removing them from the working medium vapor space. It must be capable of binding as much inert gas or vapor as is released in the sorption system through outgas sing or chemical reaction of the substances and materials contained therein. As a result, only a limited quantity of inert gas or vapor can occur in a hermetically sealed sorption system, and usually at the beginning of the sorption cycles at that. The binding agent need only bind this specific quantity of inert gas within this time period. As a matter of principle, all substances that are capable of binding inert gases or vapors occurring in a sorption system are suitable as binding agents. However, the binding agent should be capable of not re-releasing the bound inert gas even in the event of system-related fluctuations in temperature. Since most binding agents tend to do so at high temperatures, the binding agent should be applied in a place where the temperatures are as low as possible and that are subject to only small temperature fluctuations. In a sorption system, the highest temperatures occur in the sorption agent container during sorption and desorption. According to DE 44 44 252 B4, the binding agent is applied in an area in which there are relatively lower system temperatures, such as in the condenser, vaporizer or collecting receiver.

However, in the prior art, there is no coordination of the removal of the foreign gases with the mode of operation of the sorption machine.

It was therefore the object of the invention to provide a method which ensures removal of an inert gas from an inert gas trap during continuous operation of a sorption machine, particularly an adsorption machine, while ensuring improve control of the removal.

DESCRIPTION

The object is achieved by the main claim. Advantageous embodiments follow from the subclaims.

In a first preferred embodiment, the invention concerns a method for removing a foreign gas from a sorption machine, wherein the sorption machine comprises at least

-   -   one adsorber and one desorber, or one adsorber-desorber unit, or         one adsorber and one desorber,     -   one vaporizer and one condenser, or one vaporizer-condenser         unit,     -   one working medium,     -   one restrictor element and     -   one inert gas trap,         wherein         the inert gas trap comprises at least one cooling element and         one discharge element, the method comprising the following         steps:     -   a. Cooling of the inert gas trap by the cooling element to a         temperature that is lower, equal to or nearly equal to the         temperature of the condenser;     -   b. Introduction of a vaporous working medium from the desorber         or the adsorber-desorber unit into the condenser, the working         medium condensing at least partially in the condenser and         foreign gas collecting in the condenser;     -   c. Opening of a restrictor element arranged between the         condenser and the inert gas trap, the foreign gas and vaporous         working medium flowing out of the condenser into the inert gas         trap;     -   d. Heating of the inert gas trap;     -   e. Opening of a discharge device through which the foreign gas         can flow out of the inert gas trap;     -   characterized in that     -   one of the steps is initiated by a control signal selected from         the group comprising quantity of inert gas, drop in performance,         number of cycles and/or time of operation.

Through the invention, the inert gas trap is thus activated by one of the abovementioned control signals and thereby put into operation. The removal of inert gas therefore does not occur at any point in time, but rather it is coordinated with the sorption process. This leads to an increase in performance, since the inert gas can thus be removed at an ideal point in time. In this way, a drop in performance as a result of the inert gas is prevented. By virtue of the invention, the performance of the sorption machine can therefore be increased, which ultimately leads to cost-savings.

It is especially preferred that the control signal activate the inert gas trap as soon as predefined parameter values are reached. These parameter values relate either to the quantity of inert gas, performance, number of cycles or hours of operation. The quantity of inert gas is preferably reflected by the inert gas partial pressure.

In particular, in terms of the invention, the condenser can be present as a separate condenser or in a combined vaporizer/condenser unit.

A desorber in terms of the invention is particularly present either as a separate desorber or in an adsorber-desorber unit.

In terms of the invention, an “inert gas trap” preferably refers to a device for removing inert gas from a sorption machine, particularly an adsorption machine, and especially preferably an adsorption refrigerating machine.

Inert gas can also be referred to as foreign gas. A sorption machine can also be referred to as a sorption device.

The restrictor element is preferably selected from the group comprising valves, through valves, angle valves, inclined seat valves, solenoid valves, check valves and/or floats. The restrictor element is preferably integrated into a connector and brings about a localized narrowing of the cross section of flow. Advantageously, different valves, which can be subdivided according to their geometric shape, can be integrated into a restrictor element. Through the use of the valves, the flow volume in the connectors can be metered exactly and precisely by changing the interior diameter and a reliable seal against the environment can be formed. The restrictor elements can advantageously be actuated by hand, by medium, mechanically or electromagnetically.

It is especially preferred that the restrictor element that is arranged between the inert gas trap and the condenser be a valve, solenoid valve, slider, check valves, capillary pipe and/or a membrane. These preferred restrictor elements have proven especially suitable, because opening and closing is easy even in the presence of different pressure and temperature conditions.

It is preferred that the restrictor element be provided between the condenser and the inert gas trap with a control that opens the restrictor element as soon as greater pressure occurs in the condenser than in the inert gas trap. If the restrictor element is embodied as a float, the weight of the float must be sufficient to reliably seal an opening on which or against it is resting. During the desorption phase, the float is lifted by the working medium vapor flowing into the collecting receiver. The float can be made, for example, of a plastic such as polypropylene.

Moreover, it is preferred that a temperature sensor be arranged on the condenser and/or a pressure sensor on the condenser and/or desorber or the adsorber-desorber unit, the control signal depending on the measured values of the pressure and/or temperature sensor.

It is especially preferred that the quantity of inert gas be determined via the inert gas partial pressure. The detection of inert gas is preferably done in the condenser and/or in the desorber. An advantageous determination of the quantity of inert gas is performed via a temperature sensor that is arranged in the condenser. Moreover, a pressure sensor is preferably used that is arranged either in the condenser and/or in the desorber. Since both containers have the same pressure at the time of measurement, it is unimportant where the pressure sensor is arranged.

That is, the temperature sensor preferably records temperature values, whereas the pressure sensor records pressure values. It is therefore especially preferred that the determination of inert gas be performed by means of a temperature and/or pressure measurement. In doing so, the measurements are performed with the abovementioned sensors. It has been shown that this is an especially precise and yet favorable method for determine the quantity of inert gas.

It is especially preferred that the temperature sensor not be arranged in the vacuum area of the condenser, but rather in such a way that the return temperature of the condenser is measured. It is therefore the outlet temperature of the working medium that is determined. The condenser is particularly a heat exchanger that is supplied externally, i.e., not on the vacuum side, with recooled medium (preferably water). Internally, i.e., on the vacuum side, the working medium (preferably water) condenses on its surface. Three temperatures are of importance here: the flow and return temperature of the recooled medium (external) and the temperature of the condensed working medium (condensate, vacuum side). For the determination of the inert gas, it is preferred that the temperature of the condensate be determined in a vacuum. However, since it is complicated to measure that temperature, it is preferably determined indirectly through the return temperature of the condenser.

Thus, the temperature in the vacuum area can be determined indirectly by measuring the outlet temperature. Especially preferably, the temperature measurement is taken when the condenser is not providing its full output. This can preferably be in the second half of a cycle, for example. This embodiment is especially advantageous because especially accurate measured values van be generated in this way, thus enabling a very precise determination of the quantity of inert gas.

The vapor pressure of the working medium is preferably determined for the temperature of the condenser. This value is subtracted from that measured in the desorber and/or condenser. If no inert gas were present, the difference would be equal to zero. The pressure difference therefore corresponds to the inert gas partial pressure.

This determination of the quantity of inert gas via the pressure and temperature measurement has proven especially advantageous, since it enables very precise values to be obtained. What is more, it is a simple measurement for which no expensive devices are required.

It is therefore preferred that the activation of the inert gas trap be done by means of a control signal, with the control signal depending on the inert gas partial pressure. Parameter values for the inert gas partial pressure are preferably determined which act as thresholds, the exceeding of which leads to the activation of the inert gas trap via the control signal. The values for these thresholds depend above all on the size of the sorption machine as well as on the particulars of the device. Thus, the type of adsorption or absorption agent also determines the level of the threshold.

It is advantageous if the determination and removal of inert gas is done while the sorption device is running, especially preferably of an adsorption refrigerating machine. Especially preferably, the inert gas trap is activated or switched on when a certain quantity of inert gas, that is, a certain inert gas partial pressure is reached. The coordination of the removal of the foreign gases with the mode of operation of the sorption device offers an advantage compared to the inert gas trap without this control element, since better sorption performance can now be achieved. Preferably, the inert gas trap is already activated at an inert gas partial pressure that has not yet led to a drop in performance, or only to a small drop in performance. The performance, preferably the cooling performance is thus always maintained in an effective range. In the prior art, this was not possible in such a simple and precise manner.

Another preferred method for activating the inert gas trap is a performance-dependent control signal. This signal is influenced by the drop in performance. The drop in performance is preferably determined through a measurement at the vaporizer. This measurement is preferably performed using a temperature sensor. This temperature sensor measures the temperature of the incoming and outgoing working medium. If the temperature difference drops, this is an indication of a drop in performance.

A threshold is now established for a preferred embodiment of the invention after which the inert gas trap is activated. In this way, the performance, preferably the cooling performance, can be prevented from being low over an extended period of time. Especially preferably, the threshold is selected such that the inert gas trap is activated as soon as a measurable drop in performance occurs.

The use of the number of cycles as the activation signal is also preferred. The number of cycles of the sorption device is meant. This embodiment can also be advantageous. It is a statistical activation signal. Therefore, no measurement is taken of certain parameters using sensors, but rather a number of cycles is established as the threshold. When this number of cycles is reached, the inert gas trap is activated by means of the abovementioned steps. The advantage of this method is, above all, the simplicity of implementation. For instance, no special sensors need be installed. This method is particularly well suited to sorption machines that are already in operation and for which empirical data are available. However, it can also be preferably for the optimum number of cycles to be determined by means of pressure and temperature measurements. In that case, it is checked on the basis of the previously described inert gas determination at what number of cycles the inert gas thresholds were reached. The control signal is then based only on the number of cycles. It is no longer necessary to measure temperature and pressure.

The situation is similar with the use of time of operation as the activation signal. This, too, is an embodiment that can be implemented with particular ease in existing processes. As with the use of the number of cycles, a measurement of pressure and temperature can be taken before using the time of operation. It is thus possible to determine the most suitable time of operation on the basis of the inert gas determination. However, this is only a preferred variant. It is also possible to determine the most suitable time of operation by other means, thus eliminating the need for additional sensors.

The determination of the threshold according to number of cycles or time of operation depends on many factors. Among other things, the type of the adsorption or absorption agent is important. The size of the sorption device also plays an import role. A person skilled in the art knows how to establish the optimum number of cycles or hours of operation without inventive step.

It is especially preferred that step d., i.e., the heating of the inert gas trap, be initiated by the control signal and the sequence of the steps begin at step d. The preferred sequence is therefore step d, step e, step a, step b, step c, step d, step e.

Even though no inert gas has yet been fed from the condenser into the inert gas trap at the time of step d, this starting point is preferred. Starting at step d offers the advantage that inert gas that might have gotten into the inert gas trap from the environment is first evacuated. Inert gas may have gotten into the inert gas trap especially if the inert gas trap has not been operated for an extended period. As a result, ambient air may have happened to penetrate into the inert gas trap. By starting at step d, additional inert gas is thus prevented from getting into the system. The inert gas trap is therefore first evacuated as a precaution before step a begins. This embodiment has proven to be especially preferred, since this prevents additional inert gas from getting into the device that would then have to be removed.

The method preferably always ends with step e.

The present application includes the disclosed content of W02012069048. That application concerns a “Vacuum container for removing foreign gases from adsorption refrigerating machine.” The vacuum container described therein is a preferred embodiment of the inert gas trap in terms of the invention. However, the novel method according to the invention is not limited to adsorption devices. After all, the problem of the removal of foreign gases is just as relevant to absorption, for example. The method according to the invention can therefore be implemented in all sorption machines with an inert gas trap.

It is especially preferred for the working medium to be a refrigerant, preferably water.

The inert gas trap can also preferably run a certain number of cycles/procedures. The sequence of steps a to e is preferably repeated multiple times.

The number of repetitions depends on the size of the inert gas trap. 10 to 150 repetitions are preferred, for example, and 50 to 100 repetitions are especially preferred. 75 repetitions are very especially preferred. If the inert gas trap is large enough, however, one pass through the steps is also sufficient in order to completely remove the inert gas. A person skilled in the art knows what number of repetitions is especially preferred for the respective configuration of the inert gas trap and sorption device.

It is both preferred that any small quantity of inert gas be removed immediately or to postpone removal until a higher threshold is reached, and the inert gas trap is activated only then. This applies to all of the abovementioned parameters. Where the appropriate threshold lies depends, in turn, on many individual factors and cannot be generalized.

It has been shown that it is especially advantageous to make the control of the inert gas trap independent of the quantity of inert gas in the sorption device. To determine the inert gas in the case of a cycling sorption device, especially an adsorption refrigerating machine, the point in time at which the determination is made is important, and the determination is based on at least one of the following criteria:

-   -   Inert gas determination at the end of the cycle and/or     -   Inert gas determination in the middle of the cycle and/or     -   Inert gas determination upon conclusion of the condensation         process and/or     -   Determination of the average quantity of inert gas over several         seconds at the end of the cycle and/or     -   Determination of the average quantity of inert gas over the         entire cycle.

Determination of the quantity of inert gas in the middle or toward the end of the cycle is especially preferred. When the optimum point in time for determining the quantity of inert gas is also depends on the sorption device being used. A person skilled in the art is capable of executing the invention such that they are able to determine the appropriate point in time for determining the quantity of inert gas depending on the sorption device. For example, there are sorption devices in which a portion of the inert gas has already flowed to the vaporizer toward the end of the cycle. In such devices, the end of a sorption cycle is therefore not the optimum point in time for determining the inert gas, since not all of the inert gas is in the condenser by then.

At the beginning of the cycle, strong condensation is still occurring, so the condenser works and a larger quantity of vapor is produced. At such a time, the inert gas cannot be determined particularly well in some devices, so the middle to the end of a cycle tends to be suitable for determining the inert gas in such sorption devices.

It is especially preferred that the quantity of inert gas, that is, the inert gas partial pressure, be determined over a certain time period by means of several successive measurements. The determination of 5 to 100 values in a period of 5 to 150 seconds is preferred above all. The measurement of 30 to 75 values in 10 to 25 seconds is very especially preferred. An average is preferably formed from these values which then determine the quantity of inert gas. By forming the average from several successive measurements, small fluctuations are equaled out, and the quantity of inert gas can be determined especially accurately.

The method of the invention therefore includes a control concept in which the inert gas trap is activated by a control signal, thus establishing when the inert gas flows out. As a result, the entire sorption process can be improved, and increased performance is achieved.

It is especially preferred that the novel control concept be used together with the inert gas trap according to W02012069048. Such an inert gas trap can also be described as a vacuum container for a sorption device, characterized in that the vacuum container is connected via vapor-open connection means to a condenser unit of a sorption refrigerating machine and the container has a discharge device and at least one component for locking or regulating the flow of fluids.

Especially preferred is the method for removing a foreign gas from an adsorption refrigerating machine, comprising at least one adsorber/desorber unit, one vaporizer/condenser unit and one vacuum container (preferably inert gas trap) having at least one cooling element, the method comprising the following steps:

-   -   a. Cooling of the vacuum container by the cooling element to a         temperature that is lower, equal to or similar to the         temperature of the condenser unit;     -   b. Introduction of a vaporous working medium from the desorber         unit into the condenser unit, the refrigerant condensing at         least partially in the condenser unit and inert gas collecting         in the condenser;     -   c. Opening of a component for blocking or regulating the flow of         fluid arranged between the condenser unit and the vacuum         container, the inert gas and vaporous refrigerant flowing out of         the condenser unit into the vacuum container;     -   d. Heating of the vacuum container;     -   e. Opening of a discharge device through which the inert gas can         flow out of the vacuum container;         the activation of the vacuum container occurring by means of a         control signal selected from the group comprising quantity of         inert gas, drop in performance, number of cycles and/or time of         operation.

In W02012069048, the inert gas trap is referred to as a vacuum container. This vacuum container is preferably an inert gas in terms of the invention.

By virtue of the invention, this method is now being supplemented with a control concept that establishes certain activation signals on the one hand and controls the activation of the inert gas trap on the other hand.

EXAMPLE

The invention will be explained below with reference to figures without being limited thereto.

FIG. 1 shows a preferred embodiment of the inert gas trap 1, which is connected a condenser unit 8. The condenser unit 8 and the inert gas trap 1 are under vacuum. In addition to the vaporous working medium, inert gas is also located in the condenser unit 8. In one embodiment, the inert gas trap 1 contains only liquid working medium 7 and water vapor (minimum quantity or no inert gas at all). The connection means with a valve 2 opens, and the inert gas with vaporous working medium flows into the inert gas trap 1. For this purpose, a pressure difference between inert gas trap 1 and condenser unit 8 is advantageous. The pressure difference is preferably achieved by cooling the inert gas trap 1 with a cooling element 4.

When the foreign gas is to be removed from the inert gas trap 1, the connection means preferably closes with a valve 2, and the inert gas trap 1 is particularly heated with a heating element. When the pressure in the inert gas trap 1 lies above the ambient pressure, the discharge device 3 opens, and water vapor and inert gas flow into the surroundings. Another possibility for cooling the inert gas trap 1 consists in opening the connection means with a valve 2 and 6. Liquid working medium flows via the connection means with a valve 6 into the inert gas trap 1, vaporizes and flows via the connection means with a valve 2 back to the condenser unit 8. As a result, the inert gas trap 1 is cooled. It is also preferred that additional cooling of the inert gas trap 1 be achieved through the introduction of cold refrigerant from the condenser unit 8. For this purpose, a connection can exist between condenser unit 8 and inert gas trap 1.

FIG. 2 shows a preferred adsorption refrigerating machine 12 with inert gas trap 1. The adsorption refrigerating machine 12 preferably has a condenser unit 8, an adsorber unit 9, a desorber unit 10 and a vaporizer unit 11. The inert gas trap 1 removes foreign gas from the condenser unit 8 of the adsorption refrigerating machine 12. The foreign gas can be removed through a heating element from the inert gas trap 1 by means of overpressure in the inert gas trap 1, whereby the inert gas is released through a discharge device 3. The inert gas trap 1 is preferably connected by connection means 2 with controlled valve or non-return valve to the condenser unit 8. During the operation of the adsorption refrigerating machine 12, the inert gas collects primarily in the condenser unit 8.

It is preferred here that the inert gas trap 1 be heated when a certain threshold for the inert gas partial pressure has been reached. An example of control based on the determination of inert gas is shown below:

Typical temperature in the condenser 30° C. Vapor pressure of the working medium (preferably water) at 30° C.→42.4 mbar Measured pressure via the pressure sensor in the desorber/condenser is at 55 mbar

Inert gas partial pressure: “measured pressure” minus “vapor pressure working medium”→55 mbar-42.4 mbar=12.6 mbar

Without inert gas, the measured pressure would be equal to the vapor pressure calculated from the temperature. The difference corresponds to the inert gas partial pressure.

The value of 12.6 mbar therefore indicates that inert gas is present in the sorption device. If the threshold is 12.6 mbar or less, the inert gas trap is now activated.

LIST OF REFERENCE SYMBOLS

1 inert gas trap

2 connection means to the condenser unit

3 discharge device

4 cooling element

6 additional connection means to the condenser unit

7 liquid working medium

8 condenser unit

9 adsorber unit

10 desorber unit

11 vaporizer unit

12 adsorption refrigerating machine

13 connection means to the vaporizer unit 

1. A method for removing a foreign gas from a sorption machine, wherein the sorption machine comprises at least one adsorber and one desorber, or one adsorber-desorber unit, one vaporizer and one condenser, or one vaporizer-condenser unit, one working medium, one restrictor element, and one inert gas trap, wherein the inert gas trap comprises at least one cooling element and one discharge element, the method comprising: a) cooling of the inert gas trap with the at least one cooling element to a temperature that is lower, equal to or approximately equal to a temperature of the condenser; b) introducing the working medium, which is vaporous, from the desorber or the adsorber-desorber unit into the condenser, the working medium condensing at least partially in the condenser and the foreign gas collecting in the condenser; c) opening a restrictor element arranged between the condenser and the inert gas trap, the foreign gas and the working medium flowing out of the condenser into the inert gas trap; d) heating the inert gas trap; e) opening a discharge device through which the foreign gas can flow out of the inert gas trap; wherein one of a) to e) is initiated by a control signal selected from the group consisting of quantity of inert gas, drop in performance, number of cycles, time of operation and a combination thereof.
 2. The method of claim 1, wherein step d) is initiated by the control signal and the method begins sequentially at d).
 3. The method of claim 1, wherein the control signal activates the inert gas trap as soon as predefined parameter values are reached.
 4. The method of claim 1, wherein a quantity of the inert gas is determined via a temperature and/or pressure measurement.
 5. The method of claim 1, wherein a temperature sensor is arranged on the condenser and/or a pressure sensor is arranged on the condenser and/or on the desorber or on the adsorber-desorber unit, the control signal depending on a quantity of the inert gas from measured values of the pressure and/or temperature sensor.
 6. The method of claim 1, wherein a) to e) are repeated in sequence several times.
 7. The method of claim 1, wherein a the quantity of inert gas is determined at the end or in the middle of a cycle.
 8. The method of claim 1, wherein a quantity of the inert gas is determined upon conclusion of the condensation process.
 9. The method of claim 1, wherein the quantity of inert gas is determined over several seconds at the end of a cycle or the average quantity of inert gas is determined over the entire cycle.
 10. The method of claim 1, wherein the sorption method is an adsorption method.
 11. The method of claim 1, wherein the working medium is a refrigerant.
 12. The method of claim 11, wherein the refrigerant is water. 